Reduced growth with increased quotas of particulate organic and inorganic carbon in the coccolithophore <i>Emiliania huxleyi</i> under future ocean climate change conditions

• Main Authors: Y. Zhang, S. Collins, K. Gao
• Format: Article
• Language: English
• Published: Copernicus Publications 2020-12-01
• Series: Biogeosciences
• Online Access: https://bg.copernicus.org/articles/17/6357/2020/bg-17-6357-2020.pdf

<p>Effects of ocean acidification and warming on marine primary producers can be modulated by other environmental factors, such as levels of nutrients and light. Here, we investigated the interactive effects of five oceanic environmental drivers (<span class="inline-formula">CO₂</span>, temperature, light, dissolved inorganic nitrogen and phosphate) on the growth rate, particulate organic carbon (POC) and particulate inorganic carbon (PIC) quotas of the cosmopolitan coccolithophore <i>Emiliania huxleyi</i>. The population growth rate increased with increasing temperature (16 to 20 <span class="inline-formula">^∘C</span>) and light intensities (60 to 240 <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">µ</mi><mi mathvariant="normal">mol</mi><mspace linebreak="nobreak" width="0.125em"/><mi mathvariant="normal">photons</mi><mspace linebreak="nobreak" width="0.125em"/><msup><mi mathvariant="normal">m</mi><mrow><mo>-</mo><mn mathvariant="normal">2</mn></mrow></msup><mspace width="0.125em" linebreak="nobreak"/><msup><mi mathvariant="normal">s</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="104pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="5ccacc25bf51b8bccd52aa3591eec796"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-17-6357-2020-ie00001.svg" width="104pt" height="15pt" src="bg-17-6357-2020-ie00001.png"/></svg:svg></span></span>) but decreased with elevated <span class="inline-formula"><i>p</i></span><span class="inline-formula">CO₂</span> concentrations (370 to 960 <span class="inline-formula">µatm</span>) and reduced availability of nitrate (24.3 to 7.8 <span class="inline-formula">µmol L⁻¹</span>) and phosphate (1.5 to 0.5 <span class="inline-formula">µmol L⁻¹</span>). POC quotas were predominantly enhanced by the combined effects of increased <span class="inline-formula"><i>p</i></span><span class="inline-formula">CO₂</span> and decreased availability of phosphate. PIC quotas increased with decreased availability of nitrate and phosphate. Our results show that concurrent changes in nutrient concentrations and <span class="inline-formula"><i>p</i></span><span class="inline-formula">CO₂</span> levels predominantly affected the growth, photosynthetic carbon fixation and calcification of <i>E. huxleyi</i> and imply that plastic responses to progressive ocean acidification, warming, and decreasing availability of nitrate and phosphate reduce the population growth rate while increasing cellular quotas of particulate organic and inorganic carbon of <i>E. huxleyi</i>, ultimately affecting coccolithophore-related ecological and biogeochemical processes.</p>